1. Introduction
Recently, prefabricated building (PB) has aroused more interest due to its advantages of improving quality control, reducing technical labor force, shortening construction time, reducing material waste, etc. [
1,
2,
3]. In view of these advantages, PB has been considered to be a modern sustainable construction method that can replace the scattered, low-level and inefficient handicraft mode [
4]. China, characterized by rapid urbanization [
5], is vigorously using PB to achieve sustainable construction [
6]. Currently, the Chinese government has mandated that 15% (by building floor area) of the nation’s annual new buildings will be PB by 2020, and this will increase to 30% by 2025 [
7]. With the introduction of promoting policies in various regions [
6], an extremely large PB market is being born in China. However, for China, a developing country, the promotion of PB may be challenging. It is reported that the advantages of PB are difficult to achieve due to lack of knowledge and experience [
8], non-standardized design [
9], inefficient collaboration [
9], poor communication [
10], and fragmented construction process [
11]. Some studies indicated that the current construction processes are geographically and organizationally fragmented because some of the tasks (e.g., manufacturing and preassembly of some building components, modules, and elements) have moved to the factory [
1,
12,
13,
14,
15]. Specifically, the functional modules of the building are decomposed into components for production and assembled on site, which adds a large number of physical interfaces that need seamless connection, actually increasing the complex interface issues. In addition, due to the participation of more stakeholders (e.g., offsite manufacturers, transporters, and local authorities), PB faces more organizational interface issues [
16]. According to Gibb, G.F. and Pavitt, T.C. the fragmented construction process and greater number of involved stakeholders lead to complex interface issues, and effective management of these issues is the key to PB success [
17,
18].
Morris, P.W.G proposed the concept of interface management while studying the issues caused by the fragmentation between construction activities [
19]. Subsequent studies also proved the potential of interface management in construction project management. For example, interface management was adopted for improving the build process, thereby reducing rework and the total duration by identifying and tracking interfaces [
20]. For temporary construction projects, the improvement of interface transparency is conducive to the definition of responsibilities and authority [
21]. Increased permeability of organizational interfaces enables participants to scan the environment, obtain work and resources, and respond appropriately and quickly to change [
22]. Through the case analysis of 45 large construction projects, it is also reported that interface management practices can effectively alleviate the negative impact of project complexity [
23]. Accordingly, given the advantages of interface management in the construction industry, the number of studies of interface management in the PB field are gradually increasing. However, interfaces in PB are usually more complex, and it is more critical that they be managed, because they are highly fragmented in terms of geography and organization [
24]. In the book “
Off Site Fabrication-Prefabrication, Preassembly and Modularisation”, Gibb, G.F. demonstrated the need to bring interface management into PBPs to deal with the complex interface issues [
18]. Pavitt, T.C. et al. also discussed the need for interface management within PBPs, and categorized the interface management of PBPs into physical, contractual, and organizational groups [
17,
25]. Overall, previous studies defined the concept of interface management, analyzed the importance of interface management to construction projects, put forward some methods and strategies for interface management, and discussed the potential of the interface management applications in PBPs. These studies provide a theoretical basis for the interface management of PBPs. However, the early studies on interface management of PBPs remained at the conceptual level, mainly discussing the necessity and feasibility of interface management in the construction process of prefabricated construction projects. It was not until recent years that scholars begin to pay attention to the specific interface issues in PBPs. For example, relevant studies have found that early involvement of the contractor in the design phase and communication with all parties is critical to interface management [
26]. Standardization of physical interfaces can reduce the interdependence between component installation activities performed by different subcontractors [
27]. Appropriate interface management can optimize the module design of components and provide the most concise assembly scheme [
28]. As a result of the progress of information technology, building information modeling (BIM) is also being employed to improve the interface management of design–production interfaces, which can not only improve the traditional architectural interface, information sharing, and efficiency in the process of project tracking, but can also optimize interface information sharing in the process of design, manufacture, and installation, promoting better coordination among all participants [
29].
The above work provides the research basis and theoretical inspiration for this study. However, most interface management-related studies are based on traditional cast-in-situ projects or undifferentiated types of construction projects. Few PBP interface management-related studies focus on methods and strategies for interface improvement, and lack an in-depth examination of the influencing factors. Most of the influencing factors of interface management mentioned in existing studies are obtained by qualitative reasoning of the relevant authors, and lack the support of quantitative analysis methods. Moreover, the research on interface management is relatively scattered, and there is no unified classification standard for the influencing factors. To compensate for these limitations, the present study aimed to explore the critical factors influencing the interface management of PBPs by combining qualitative and quantitative methods. The results provide a systematic list of influencing factors for PBP interface management, which is not available in previous studies.
5. Discussion
Combining the connotation and reflection characteristics of the internal factors of each cluster, it can be found that although most of the factors’ reflection characteristics in the same cluster have high consistency, the factors in Cluster (1) “information communication, trust and cooperation” have differences in their reflection characteristics. Therefore, in this study, Cluster (1) was divided into “information communication” and “trust and cooperation”. Finally, the seven clusters can be renamed:
Cluster 1: Information communication;
Cluster 2: Trust and cooperation;
Cluster 3: Technical and managerial ability;
Cluster 4: Organizational integration;
Cluster 5: Standardization;
Cluster 6: Technical environment;
Cluster 7: Contract management.
5.1. Information Communication (Cluster 1)
This cluster consists of three critical factors: (1) completeness and accuracy of information, (2) timeliness of information communication, and (3) degree of information sharing. In the existing literature, information communication was one of the most common and critical influencing factors in interface management of construction projects [
75,
91]. Valuable data, information, knowledge, experience, and ideas exist in the various organizations of the construction project, and cross-interface linkages must be established between organizations to ensure the effectiveness of information communication [
52].
PBPs involve data information of design, procurement, production, transportation, construction, and other processes. Therefore, the process of information transfer is very complex, and the integrity of information must be considered. Defects in the expression of early design information usually lead to the lack of integrity of the design information, and it is difficult for component manufacturers and constructors to use the design information [
79]. Project information is transferred across time, space, and the organization [
74]. Due to differences in expertise among different stakeholders, the recipients may exaggerate or distort the information when transmitting it to other participants [
67]. Therefore, managers should pay more attention to the accuracy of information across interfaces. The application of BIM technology in PBPs is a good example. BIM is committed to addressing the omission and asymmetry of information across the interface through a standardized information model [
78,
92,
93], which can ensure the integrity and accuracy of information. In addition, the timeliness of information communication is also identified as a challenge of interface management [
57,
72,
73]. The more timely the information communication, the higher the efficiency and value of information use. Due to the spatial and temporal dispersion of PBP participants, the timeliness of information communication should be focused on to avoid the emergence of information silos. Similarly, information sharing is a key concern throughout the construction industry and is a crucial factor in the effectiveness of interface management. The main methods of handling interface information in construction projects include sharing drawings and specifications, face-to-face meetings, oral presentations, telephone conversations, and email [
23]. Due to the spatial difference between factory, site, and office, the interface information communication is inefficient. Information sharing can enhance the accuracy and timeliness of information transmission to a certain extent and ensure the seamless connection of information to the greatest extent. PBP is highly integrated in the production organization, and has higher requirements for information sharing. With the development of information technology, Radio Frequency Identification (RFID), BIM and other advanced technologies improve the degree of information sharing [
94,
95,
96], and provide technical means for smooth information across the interface.
5.2. Trust and Cooperation (Cluster 2)
The “trust and cooperation” cluster consists of four critical factors that involve (1) the cooperative attitude of participants, (2) understanding and trust between organizations, (3) communication and learning between organizations, and (4) degree of participant involvement in design. With the development of prefabricated building technology, “trust and cooperation” is considered to be critical factor for effective communication between organizations, conflict resolution, and supply chain integration [
70,
97,
98]. Housing industrialization alliances and prefabricated building alliances based on trust and cooperation have emerged in China. The participants in these alliances must maintain a high degree of trust and cooperation to maintain their stability. Existing research conclusions also confirm the importance of “trust and cooperation” in interface management of construction projects [
22,
52,
54].
Many studies show that different cooperative attitudes are the root cause of interface conflicts in construction projects [
44,
50,
54]. Due to the larger number of participants, higher professional barriers, and more complex conflicts of interest in PBPs, differences in cooperation attitudes may lead to more serious interface problems. The better interface relationship of PBPs can be ensured by enhancing the cooperative intention and attitude of participants. Understanding and trust have a direct positive effect on interface management, and can have an indirect positive effect on interface management by enhancing information communication between organizations [
52]. Although no study directly mentioned the influence of “understanding and trust” on PBP interface management, some scholars expressed similar views. For example, Xue, H. believed that understanding and trust can improve the relationship between the participants of PBPs [
81]. Communication learning is one of the decisive factors for the performance of temporary organizational interface management [
99]. The communication and learning between organizations can effectively promote the diffusion of prefabricated building technology, improve the level of professional knowledge of participants, narrow professional differences, and thus reduce the probability of interface conflicts. Since prefabricated components or parts are difficult to change after installation, early communication between participants often leads to interface problems during the production, construction, and installation phases. Therefore, participants (designers, manufacturers, and constructors) should be encouraged to participate in collaborative design as early as possible in PBPs [
26,
70].
5.3. Technical and Managerial Ability (Cluster 3)
Six critical factors belong to this cluster: (1) accuracy of design, (2) experience and level of participants, (3) reasonableness of the production and construction plan, (4) technical level of operators, (5) timeliness of component production and supply, and (6) tracking of component production and installation process. This cluster accounts for 11.534% of the total variance explained among all of the critical factors.
The accuracy of the design reflects the technical ability of the designer. Inaccurate and non-standard design may lead to a wrong understanding of drawings or specifications by developers and contractors, which is not conducive to interface management [
58] and even affects the compatibility between prefabricated components [
59]. Management experience and ability are the important criteria for enterprises to choose partners, and also the critical indicators for selecting participants when bidding for prefabricated construction projects [
100]. Participants with higher management experience and ability can better manage the interface because they have mastered prefabricated building techniques, and have accumulated rich experience in dealing with various interface conflicts. In addition, the impact of the operator’s technical level on interface management is mainly reflected in the physical interface. For example, the more skilled the operator, the more familiar they are with the connection structure and installation process of the component. The connection between the upstream and downstream processes can be smoothly completed to ensure the seamless connection of the physical interface in the installation process. The timeliness of component production and supply, and the tracking of component production and the installation process, can reflect the management experience and capability of the component manufacturer. Lack of storage space and traffic congestion still hamper the smooth delivery of prefabricated components. The lack of Just in Time (JIT) capability is identified as a critical risk in PBPs [
16]. Delivery delay can disrupt construction schedules and lead to ongoing interface conflicts between component producers and constructors. The tracking of component production and the installation process can ensure smooth connection of the production–construction interface. In recent years, RFID and other technologies have been widely used for this [
16,
83,
84].
5.4. Organizational Integration (Cluster 4)
This cluster consists of five critical factors related to organizational integration: (1) professional differences between participants, (2) reasonableness of organizational structure design, (3) project management mode, (4) consistency of organizational goals, and (5) cultural differences between participants. These factors reflect the overall consideration requirements of interface management for different participants in organizational structure, specialty, goals, and culture, which are consistent with the basic requirements of organizational integration. Therefore, this cluster is named organizational integration, which refers to the degree of project organization integration. This cluster accounts for 7.170% of the total variance explained among all of the critical factors.
Professional differences have been identified as the main cause of interface management problems [
67,
68]. Eliminating professional differences can effectively break down cooperation barriers. The professional differences of participants are more complex in PBPs, and interface conflicts are more likely to occur in the process of cooperation. Similarly, consistency of goals and cultural differences are often cited as critical factors in interface management research. The commitment to common goals can reduce the complexity of interface interactions in construction projects [
22]. Gibb, G.F. clearly demonstrated the importance of consistency of goals between organizations for PBP interface management [
17,
26]. Participants need a more culturally compatible environment because of their different cultural backgrounds. Otherwise, cultural differences may affect information communication, trust, and cooperation, and thus affect the interface relations between participants [
11,
65]. Because PBPs require highly integrated organizational management, managers must pay more attention to organizational structure. Similarly, scholars have carried out a large number of studies on interface management under various construction project management modes [
71,
101]. For example, integrated project delivery (IPD) [
102] and partnering [
54] emphasize the integration of organizations, consistency of goals, and long-term partnership, and they have more advantages than the traditional project management mode. Pavitt, T.C. and Gibb, G.F. also verified that adoption of the partnering mode is more able to deal with difficult interface management problems in PBPs [
17].
5.5. Standardization (Cluster 5)
This cluster accounts for 6.239% of the total variance explained among all of the critical factors, and consists of four critical factors: (1) standardization of information, (2) standardization of production and construction processes, (3) complexity of connection interfaces between prefabricated components, and (4) formal interface management process. Although these factors refer to different objects, they all focus on standardization–related issues. Notably, this cluster does not include standardization of design; the specific reasons for this are outlined in
Section 5.6.
Standardized information transfer and storage is the basis for stakeholders to realize project information sharing in their own information management systems [
76]. The expression, storage, and exchange of standardized information are helpful to coordinate interface conflicts and track interface information. In recent years, the standardized information management system has gradually been widely applied in PBPs. Standardization of production and construction processes is a critical factor in the interface management of construction projects [
47] and the necessary condition for PBP implementation. Chen, Q. believes that standardizing the technological process of various interfaces in construction projects can reduce the uncertainty of interface management [
64]. Therefore, it can be concluded that improving standardization of production and construction processes is also an effective way to reduce interface conflicts and risks of PBPs. In addition, the complexity of connection interfaces between prefabricated components is also a critical factor in interface management. Zhang, Y. found that this factor makes various components or parts prone to conflict when matching [
103]. The complex interfaces and dependencies between many different components or parts may lead to installation difficulties for field workers [
25]. Therefore, standardization of physical interfaces can be improved by reducing complexity. Similarly, some scholars believe that formal the interface management process can effectively alleviate the adverse effects of project complexity [
23] and improve the behaviors of participants [
53]. It is necessary to develop a formal interface management process to deal with more complex interface management problems.
5.6. Technical Environment (Cluster 6)
This cluster accounts for 5.252% of the total variance explained among all of the critical factors, and consists of three critical factors: (1) technological innovation, (2) degree of perfection of standards and specifications, and (3) standardization of design. In contrast to other clusters, it seems that technological innovation, standard specification, and design standardization cannot be easily summarized in the same cluster. However, all three critical factors reflect problems with the technology itself and are the basis of the technology on which PBPs rely. These problems are not immediately transferable to the subjective will of the project participants. Therefore, this study believes that Cluster 6 is the external manifestation of the technical environment, which directly affects project construction and has nothing to do with the project itself.
The application of new technology (especially transformative technology) is often accompanied by technological uncertainty, and, due to the lack of knowledge and experience, users have to seek technology and knowledge support across interfaces [
104]. In recent years, the research focus of prefabricated building technology innovation in China has mainly included component connection and installation integration; that is, the interaction of prefabricated components with physical interfaces is the focus of the current research. In addition, the role of PB-related technologies (such as BIM) in improving interface management has also been affirmed [
29]. Based on this, this study confirms the impact of technological innovation on interface management. The importance of technical standards and specifications for the implementation of PB is the consensus of academia and industry. With the large-scale popularization of PB, technical standards and specifications have been gradually improved in recent years. These standards and specifications are the basic reference for design, production, construction, product delivery, and acceptance of construction projects. Therefore, well-developed standards and specifications can help participants clarify technical requirements, standardize work processes, and deliver qualified products. At present, the low standardization of design is a common problem faced by PB technology, rather than being only a problem of a project or design institute itself. From this perspective, we can understand why this factor is clustered into the technical environment. The rules of standardized components or parts are uniform and reproducible, thus reducing the complexity of entity interface tasks. Furthermore, the interface has strong interoperability between different professions, thus reducing the degree of dependence between building component installation activities [
61]. Therefore, it is of great significance to improve the standardization of design for interface management in PBPs.
5.7. Contract Management (Cluster 7)
This cluster is responsible for 4.605% of the total variance explained among all critical factors, and contains only two critical factors: (1) definition of work content and scope, and definition of responsibility–power–benefit. The above two critical factors are the main content of contract management, so this cluster is named contract management. Notably, these two factors have nevertheless received much attention in construction project interface management studies [
17,
26,
57,
71,
72], and have been mentioned in the PBP interface management literature [
17,
26].
PBPs involve professional and complex contractual relationships. The contract should clearly define the content and scope of work, and the boundaries of each profession should be clearly divided and rationally overlapped. This can prevent participants from avoiding responsibilities due to ambiguous interfaces and prevent related interfaces from becoming management blind spots. To a certain extent, the definition of work content and scope also affects the attribution of responsibility–power–benefit. For example, in some highly integrated management modes, project managers can coordinate the consistent goals among organizations through responsibility–power–benefit, and pursue the optimization of the overall goals of the project. In this case, the definition of responsibility–power–benefit needs to remove the constraints of work content and scope, and serve the overall goal of the project. Otherwise, project participants may not cooperate effectively in order to avoid risks. Therefore, in order to ensure the rationality of the responsibility–power–benefit interface in PBPs, it is necessary to clarify the responsibilities and obligations of all parties, and fully mobilize the enthusiasm of the participants to cooperate on the interface.
6. Conclusions and Suggestions
Compared with traditional cast-in-situ projects, PBP interface management needs to consider more complex elements. Based on a literature review, questionnaire survey, and expert interviews, this paper identified and examined the list of factors influencing interface management of PBPs. The 27 factors were further analyzed by factor analysis, thus providing a clear understanding of the interrelationship among these factors.
The results show that the most critical factor among the 27 influencing factors is the accuracy of design, followed by the timeliness of information communication, the timeliness of component production and supply, the standardization of design, and the definition of work content and scope. These results are helpful for managers to improve their interface management ability. In addition, using factor analysis, the underlying relationships among the 27 critical factors were further explored, and the factors were categorized into seven clusters: (1) information communication, (2) trust and cooperation, (3) technical and management capability, (4) organizational integration, (5) standardization, (6) technical environment, and (7) contractual management. This study enriches the development of research in the field of interface management in the construction industry and contributes to the existing body of knowledge. The results are expected to help managers to deeply understand the causes of various interface problems in PBPs and offer useful guidance for the sustainable and healthy development of PB technology.
Based on the above research conclusions, the following suggestions are proposed for the interface management of PBPs: First, stakeholders should establish long-term stable partnerships and be encouraged to use information technology (e.g., BIM, RFID). This may improve communication, trust, and organizational integration, enabling better interface interactions between stakeholders. Furthermore, the training of management and technical personnel should be strengthened to enhance the technical and management capabilities of project participants. It is also necessary to emphasize the importance of contract management and clarify the relevant contract interfaces. Stakeholders without contractual relationships should establish close ties by signing partnership agreements. In addition, the integration of design, production, and construction should be strengthened. The standardization of information, construction technology, and management procedures throughout the life cycle can ensure the integration of design, production, and construction. Finally, the government should play a greater role in the development of the PB industry to improve interface management, such as by promoting collaborative innovation, establishing information and technology standards, and optimizing the technological environment.
In addition to improving the interface management effect, these suggestions also contribute to the sustainability of PB. For example, standardized construction processes can ensure a seamless flow from stage to stage, reducing unnecessary construction activities and waste. Improving communication, trust, and cooperation between organizations can reduce transaction costs and promote economic sustainability. Governments can also promote the use of clean energy and improve environmental sustainability by issuing green construction standards. This suggests that the improvements in the technological environment may lead to more environmental benefits.
It should be noted that the majority of respondents in this study were from prefabricated concrete building projects and did not fully cover other PBPs such as wood and steel structures. This is because the current construction form of PBPs is mainly prefabricated concrete frames. In addition, although the influencing factors were clustered, the interaction between each factor was not analyzed. In the future, we will use multiple regression analysis and other methods to deeply explore the relationship path and influence mechanism among factors. Based on this, we may also build a PBP case library and interface knowledge ontology model to provide managers with a retrieval program and analysis tool for interface management.